1. Field of the Invention
The present invention relates to a high-output laser light source which outputs pulsed light amplified by using an optical amplifier, and is applied to processing use, medical use, and so on.
2. Related Background Art
In many fields of laser processing, medical treatment, measurement or the like, there are demands for pulsed laser light having a short pulse width and a high pulse peak power and allowing for a fast repetition rate. In the laser processing field, the pulsed laser light is often implemented by Q-switching. In a Q-switched pulsed laser light source, however, there is a limit in shorter pulse generation and it is also difficult to achieve fast repetition rates because the pulse width is equivalent to a duration of time in which light travels back and forth multiple times in an optical resonator. For this reason, attention is being drawn to laser light sources using a MOPA (Master Oscillator Power Amplifier) system in which a seed light source is a pulse-modulated semiconductor laser or the like and in which an optical amplifier is located downstream thereof. It is known that when the MOPA system is adopted for the laser light source, there is an effect that it is easy to realize a high gain and stable diffraction-limited beam quality, by composing the optical amplifier part of an optical fiber amplifier wherein an optical amplification medium is an optical fiber doped with a rare earth element.
However, when the pulse operation is suspended in use of the pulsed laser light source of the MOPA system, a halt of output of pulsed light from the seed light source raises a population inversion to the extreme in the optical fiber which is the optical amplification medium included in the optical fiber amplifier and doped with the rare earth element. Therefore, an optical surge, which is a temporary increase in optical power of outputted light, can be generated upon a restart of the pulse operation. A method of blocking the pulsed laser light after the restart of output is under research, for example as described in Japanese Patent Application Laid-Open No. 2001-358087, as a method for preventing a workpiece from being irradiated with the laser light of the optical surge thus generated.